The present invention generally relates to an image display system and more particularly, to a high speed page turning control system based on a hardware window type.
Conventionally, there have been proposed image display control systems, for example, as shown in FIG. 5(a), 5(b) and 5 (c).
The control system based on a raster operation as shown in FIG. 5(a) is of a software window type. The control system is arranged so that each image information of windows A, B and C stored in a window memory 1 is once subjected to block transfer to a display memory 2, on which editing of the image surface such as positioning, overlapping, etc. for the respective windows A, B and C is effected, and thereafter, the image information is successively read out from the display memory 2 for displaying multi-windows on a CRT (cathode ray tube) 3.
In the arrangement based on a mapping table system of FIG. 5(b), each image information of windows A, B and C is stored in a window memory 4 and the address of the image information corresponding to the scanning position of a CRT 6 is outputted during scanning of the CRT 6 through successive change-over from a mapping table 5 in the form of a hardware, whereby the image information from the window memory 4 is read by time division according to said address so as to display the multi-windows directly on the CRT 6 without passing through any other memory.
Meanwhile, the control system based on clipping, as shown in FIG. 5(c), is of a software window type so arranged that code data representing the image information for the windows A, B and C as stored in a segment buffer 7 is displayed on a display memory 8, with the code data of the image information outside the windows being removed by clipping, and thus, the image information is successively read out from the display memory 8 for displaying multi-windows on the CRT 9.
However, the conventional image display control systems in FIG. 5(a), 5(b) and 5(c) as referred to above respectively have problems, as described hereinafter, in the case where the process for turning pages is to be actively represented by effecting compression display of the windows.
More specifically, in the control system by the raster operation of FIG. 5 (a), since the image information of the window memory 1 is once subjected to block transfer onto the display memory 2 for editing the image surface on said display memory 2 so as to be subsequently displayed on the CRT 3, in the case where the page turning for compression display of the windows is to be realized, it is necessary to excute the function for the block transfer while thinning-out the image information in the window region, each time when the windows are compressed, and thus, it is difficult to effect a high speed and active page turning.
Meanwhile, in the control system by the mapping table of FIG. 5(b), since the address on the window memory 4 is successively outputted through change-over from the mapping table 5 and the image information stored in this address is directly displayed on the CRT 6 by time division, it is possible to display the page at any desired position on the CRT 6 at high speeds. However, the above function is nothing but a mere page change-over display as it is, and active page turning can not be represented thereby. More specifically, in the case where the image of compressed windows is to be displayed actively, alteration of parameters showing the window regions following the compression must by effected per each frame refreshing (to display 30 to 70 images per second).
In the control system by the clipping in FIG. 5(c), owing to the arrangement that the code data representing the image information of the segment buffer 7 is drawn on the display memory 8, with the code data for the unnecessary image information being removed by clipping for subsequent display on the CRT 9, in the case where the page turning by compresed display of windows is to be realized on the CRT 9, it is required to provide a hardware to compress the code data of the segment buffer of for drawing thereof on the display memory 8 at high speeds.